The present invention relates to the production of liquid hydrocarbons, and more particularly, to the production of liquid hydrocarbons using various thermal methods. The enhanced recovery of oil and particularly heavy crude deposits has increased during recent years as a result of decreasing reserves and increasing prices. These factors make thermal recovery methods economically attractive. In thermal recovery processes using steam, two methods are used. In the first, steam is injected into the formation for a period of time after which the well is shut in and allowed to soak. Following the soaking period, the crude oil that accumulates in the well, is produced, and the process is repeated. In the second method, the steam is used to not only heat the formation, but drive the crude toward a producing well. In both of these methods the steam flows through perforations in the well casing and it is highly desirable to know the injection profile of the steam into the formation. It is, of course, desirable that the steam enter the formation in a uniform pattern and not bypass a portion of the formation and enter only a restricted portion of the formation. It would also be desirable to know the quality of the steam being injected into each portion of the formation.
Various means have been proposed for measuring the steam quality downhole in a thermal recovery process. For example, U.S. Pat. No. 4,409,825 discloses a system for obtaining a steam sample downhole to determine the quality of the steam and dissolved solids in the sample. While this method measures the quality of the steam, it does not give a profile of the steam injection into the formation since the system does not measure steam flow. Further, the system requires the insertion of elaborate equipment in the well in addition to the installation of a separate sample tube system for conveying the steam sample to the surface. Finally, this method requires that the steam flow rate be known and it thus gives no information after the first perforation zone.
While various methods are available for measuring steam quality and flow rates in pipelines and the like, all of these methods require the use of electronic circuits for producing signals that must be transmitted to a use location. It is well known that electronic circuits will not withstand the temperatures existing in downhole steam wells, i.e. 500.degree.-600.degree. F. Thus, the adaption of known methods to downhole use is not possible.